Bore Pumps, Boost Pumps and Centre Pivots

Overview

A Queensland cotton and grain farming enterprise undertook an energy audit to address inefficiencies in its irrigation system. With three bore pump suppling three centre pivots and a hand shift irrigation system, the audit identified significant opportunities for energy savings through pump replacements and the integration of solar arrays. Two bore pumps had individual boost pumps to supply the required pressure at the centre pivot which increased operating costs significantly.

Challenge

The irrigation system relied on ageing line shaft and boost pumps, which demonstrated low efficiency and consumed excessive electricity. Key inefficiencies included:
With all pumps operating on a soon to be obsolete Tariff 66, the rising costs of electricity presented a further challenge. The farm’s combined electricity usage for all three bores was 169,657kWh annually, resulting in high operational costs and greenhouse gas emissions.

Proposed Solution

  • For Bore 1: The line shaft pump was replaced with a two-stage Franklin FPS-140FS-2F submersible pump, eliminating the need for the boost pump. This upgrade increased efficiency from 50.8% to 70.2%, while reducing electricity usage by 35.9%, resulting in annual savings of 19,963 kWh.

  • For Bore 2: The line shaft pump was replaced with a three-stage Franklin FPS-140FS-3L submersible pump equipped with a Variable Speed Drive (VSD). This upgrade significantly improved efficiency, increasing it from 31.0% to 71.2%, while reducing electricity consumption by 28,572 kWh annually—a 73.4% decrease. The VSD was specifically recommended for Bore 2 to address the challenges posed by the undulating terrain, which created significant variations in the total dynamic head. Without the VSD, a single-speed pump would have resulted in fluctuating pressures and inconsistent water flow rates, making it difficult to meet the precise irrigation requirements.

  • For Bore 4: The current system will remain in operation until failure, at which point a new bore will be drilled to accommodate a pump capable of meeting the irrigation requirements. No suitable 8-inch replacement pump was identified that could meet the design specifications within the existing bore casing. The duty point analysis determined that a 10-inch pump is required to align with the centre pivot’s design specifications.
  • Install a 40kW solar array with a 30kW inverter for Bores 1 and 2, consolidating the NMIs to optimise solar energy utilisation. The 40kW solar system is projected to reduce electricity consumption by 40,019 kWh (42.3%) and lower electricity costs by $10,417 (51.8%) under Tariff 66.

  • A dedicated 40kW solar array with a 30kW inverter was recommended for Bore 4. This system reduces electricity consumption by 34,592 kWh (46.1%) and cuts electricity costs by $9,689 (60.6%) under Tariff 66.

Financial Environmental Impact

The total capital investment for these upgrades was $139,458. Collectively, the three bores achieved annual energy savings of 123,146 kWh, representing a 72.5% reduction in electricity consumption. Additionally, greenhouse gas emissions were cut by 99.7 tonnes of CO₂ each year, reinforcing the farm’s commitment to sustainability and environmental stewardship.

Conclusion

The energy audit and subsequent upgrades transformed the farm’s irrigation system, delivering substantial financial, operational, and environmental benefits. Replacing inefficient line shaft pumps with modern submersible pumps, coupled with the strategic use of Variable Speed Drives, significantly improved system efficiency and reduced electricity consumption. The integration of 40kW solar arrays further enhanced energy savings, cutting costs and lowering reliance on grid power.
Collectively, these measures resulted in an annual energy reduction of 123,146 kWh—a 72.5% decrease—while lowering greenhouse gas emissions by 99.7 tonnes of CO₂ annually. The upgrades not only addressed the inefficiencies of the ageing system but also positioned the farm for long-term sustainability and cost-effectiveness.
This project highlights the importance of tailored energy solutions, demonstrating how targeted investments in efficiency and renewable energy can meet the dual goals of reducing operational costs and improving environmental outcomes. It serves as a blueprint for other agricultural operations seeking to enhance productivity while promoting sustainability.